diff options
Diffstat (limited to 'fs/btrfs/backref.h')
| -rw-r--r-- | fs/btrfs/backref.h | 195 |
1 files changed, 173 insertions, 22 deletions
diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h index 8e69584d538d..ef6bbea3f456 100644 --- a/fs/btrfs/backref.h +++ b/fs/btrfs/backref.h @@ -7,10 +7,128 @@ #define BTRFS_BACKREF_H #include <linux/btrfs.h> +#include "messages.h" #include "ulist.h" #include "disk-io.h" #include "extent_io.h" +/* + * Used by implementations of iterate_extent_inodes_t (see definition below) to + * signal that backref iteration can stop immediately and no error happened. + * The value must be non-negative and must not be 0, 1 (which is a common return + * value from things like btrfs_search_slot() and used internally in the backref + * walking code) and different from BACKREF_FOUND_SHARED and + * BACKREF_FOUND_NOT_SHARED + */ +#define BTRFS_ITERATE_EXTENT_INODES_STOP 5 + +/* + * Should return 0 if no errors happened and iteration of backrefs should + * continue. Can return BTRFS_ITERATE_EXTENT_INODES_STOP or any other non-zero + * value to immediately stop iteration and possibly signal an error back to + * the caller. + */ +typedef int (iterate_extent_inodes_t)(u64 inum, u64 offset, u64 num_bytes, + u64 root, void *ctx); + +/* + * Context and arguments for backref walking functions. Some of the fields are + * to be filled by the caller of such functions while other are filled by the + * functions themselves, as described below. + */ +struct btrfs_backref_walk_ctx { + /* + * The address of the extent for which we are doing backref walking. + * Can be either a data extent or a metadata extent. + * + * Must always be set by the top level caller. + */ + u64 bytenr; + /* + * Offset relative to the target extent. This is only used for data + * extents, and it's meaningful because we can have file extent items + * that point only to a section of a data extent ("bookend" extents), + * and we want to filter out any that don't point to a section of the + * data extent containing the given offset. + * + * Must always be set by the top level caller. + */ + u64 extent_item_pos; + /* + * If true and bytenr corresponds to a data extent, then references from + * all file extent items that point to the data extent are considered, + * @extent_item_pos is ignored. + */ + bool ignore_extent_item_pos; + /* A valid transaction handle or NULL. */ + struct btrfs_trans_handle *trans; + /* + * The file system's info object, can not be NULL. + * + * Must always be set by the top level caller. + */ + struct btrfs_fs_info *fs_info; + /* + * Time sequence acquired from btrfs_get_tree_mod_seq(), in case the + * caller joined the tree mod log to get a consistent view of b+trees + * while we do backref walking, or BTRFS_SEQ_LAST. + * When using BTRFS_SEQ_LAST, delayed refs are not checked and it uses + * commit roots when searching b+trees - this is a special case for + * qgroups used during a transaction commit. + */ + u64 time_seq; + /* + * Used to collect the bytenr of metadata extents that point to the + * target extent. + */ + struct ulist *refs; + /* + * List used to collect the IDs of the roots from which the target + * extent is accessible. Can be NULL in case the caller does not care + * about collecting root IDs. + */ + struct ulist *roots; + /* + * Used by iterate_extent_inodes() and the main backref walk code + * (find_parent_nodes()). Lookup and store functions for an optional + * cache which maps the logical address (bytenr) of leaves to an array + * of root IDs. + */ + bool (*cache_lookup)(u64 leaf_bytenr, void *user_ctx, + const u64 **root_ids_ret, int *root_count_ret); + void (*cache_store)(u64 leaf_bytenr, const struct ulist *root_ids, + void *user_ctx); + /* + * If this is not NULL, then the backref walking code will call this + * for each indirect data extent reference as soon as it finds one, + * before collecting all the remaining backrefs and before resolving + * indirect backrefs. This allows for the caller to terminate backref + * walking as soon as it finds one backref that matches some specific + * criteria. The @cache_lookup and @cache_store callbacks should not + * be NULL in order to use this callback. + */ + iterate_extent_inodes_t *indirect_ref_iterator; + /* + * If this is not NULL, then the backref walking code will call this for + * each extent item it's meant to process before it actually starts + * processing it. If this returns anything other than 0, then it stops + * the backref walking code immediately. + */ + int (*check_extent_item)(u64 bytenr, const struct btrfs_extent_item *ei, + const struct extent_buffer *leaf, void *user_ctx); + /* + * If this is not NULL, then the backref walking code will call this for + * each extent data ref it finds (BTRFS_EXTENT_DATA_REF_KEY keys) before + * processing that data ref. If this callback return false, then it will + * ignore this data ref and it will never resolve the indirect data ref, + * saving time searching for leaves in a fs tree with file extent items + * matching the data ref. + */ + bool (*skip_data_ref)(u64 root, u64 ino, u64 offset, void *user_ctx); + /* Context object to pass to the callbacks defined above. */ + void *user_ctx; +}; + struct inode_fs_paths { struct btrfs_path *btrfs_path; struct btrfs_root *fs_root; @@ -23,17 +141,59 @@ struct btrfs_backref_shared_cache_entry { bool is_shared; }; -struct btrfs_backref_shared_cache { +#define BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE 8 + +struct btrfs_backref_share_check_ctx { + /* Ulists used during backref walking. */ + struct ulist refs; + /* + * The current leaf the caller of btrfs_is_data_extent_shared() is at. + * Typically the caller (at the moment only fiemap) tries to determine + * the sharedness of data extents point by file extent items from entire + * leaves. + */ + u64 curr_leaf_bytenr; + /* + * The previous leaf the caller was at in the previous call to + * btrfs_is_data_extent_shared(). This may be the same as the current + * leaf. On the first call it must be 0. + */ + u64 prev_leaf_bytenr; /* * A path from a root to a leaf that has a file extent item pointing to * a given data extent should never exceed the maximum b+tree height. */ - struct btrfs_backref_shared_cache_entry entries[BTRFS_MAX_LEVEL]; - bool use_cache; + struct btrfs_backref_shared_cache_entry path_cache_entries[BTRFS_MAX_LEVEL]; + bool use_path_cache; + /* + * Cache the sharedness result for the last few extents we have found, + * but only for extents for which we have multiple file extent items + * that point to them. + * It's very common to have several file extent items that point to the + * same extent (bytenr) but with different offsets and lengths. This + * typically happens for COW writes, partial writes into prealloc + * extents, NOCOW writes after snapshoting a root, hole punching or + * reflinking within the same file (less common perhaps). + * So keep a small cache with the lookup results for the extent pointed + * by the last few file extent items. This cache is checked, with a + * linear scan, whenever btrfs_is_data_extent_shared() is called, so + * it must be small so that it does not negatively affect performance in + * case we don't have multiple file extent items that point to the same + * data extent. + */ + struct { + u64 bytenr; + bool is_shared; + } prev_extents_cache[BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE]; + /* + * The slot in the prev_extents_cache array that will be used for + * storing the sharedness result of a new data extent. + */ + int prev_extents_cache_slot; }; -typedef int (iterate_extent_inodes_t)(u64 inum, u64 offset, u64 root, - void *ctx); +struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void); +void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx); int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical, struct btrfs_path *path, struct btrfs_key *found_key, @@ -43,11 +203,9 @@ int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb, struct btrfs_key *key, struct btrfs_extent_item *ei, u32 item_size, u64 *out_root, u8 *out_level); -int iterate_extent_inodes(struct btrfs_fs_info *fs_info, - u64 extent_item_objectid, - u64 extent_offset, int search_commit_root, - iterate_extent_inodes_t *iterate, void *ctx, - bool ignore_offset); +int iterate_extent_inodes(struct btrfs_backref_walk_ctx *ctx, + bool search_commit_root, + iterate_extent_inodes_t *iterate, void *user_ctx); int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info, struct btrfs_path *path, void *ctx, @@ -55,13 +213,8 @@ int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info, int paths_from_inode(u64 inum, struct inode_fs_paths *ipath); -int btrfs_find_all_leafs(struct btrfs_trans_handle *trans, - struct btrfs_fs_info *fs_info, u64 bytenr, - u64 time_seq, struct ulist **leafs, - const u64 *extent_item_pos, bool ignore_offset); -int btrfs_find_all_roots(struct btrfs_trans_handle *trans, - struct btrfs_fs_info *fs_info, u64 bytenr, - u64 time_seq, struct ulist **roots, +int btrfs_find_all_leafs(struct btrfs_backref_walk_ctx *ctx); +int btrfs_find_all_roots(struct btrfs_backref_walk_ctx *ctx, bool skip_commit_root_sem); char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path, u32 name_len, unsigned long name_off, @@ -77,10 +230,9 @@ int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid, u64 start_off, struct btrfs_path *path, struct btrfs_inode_extref **ret_extref, u64 *found_off); -int btrfs_is_data_extent_shared(struct btrfs_root *root, u64 inum, u64 bytenr, +int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr, u64 extent_gen, - struct ulist *roots, struct ulist *tmp, - struct btrfs_backref_shared_cache *cache); + struct btrfs_backref_share_check_ctx *ctx); int __init btrfs_prelim_ref_init(void); void __cold btrfs_prelim_ref_exit(void); @@ -111,8 +263,7 @@ struct btrfs_backref_iter { u32 end_ptr; }; -struct btrfs_backref_iter *btrfs_backref_iter_alloc( - struct btrfs_fs_info *fs_info, gfp_t gfp_flag); +struct btrfs_backref_iter *btrfs_backref_iter_alloc(struct btrfs_fs_info *fs_info); static inline void btrfs_backref_iter_free(struct btrfs_backref_iter *iter) { |